• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.1-6
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• 2011

Optical gain characteristics of $1.3{\mu}m$ type-II GaAsSb/InGaNAs/GaAs trilayer quantum well structures were studied using multi-band effective mass theory. The results were compared with those of $1.3{\mu}m$ GaAsSb/InGaNAs/GaAs trilayer quantum well structures. In the case of $1.3{\mu}m$ GaAsSb/InGaNAs/GaAs trilayer quantum well structure, the energy difference between the first two subbands in the valence band is smaller than that of $1.3{\mu}m$ GaAsSb/InGaNAs/GaAs trilayer quantum well structure. Also, $1.3{\mu}m$ GaAsSb/InGaNAs/GaAs trilayer quantum well structure shows larger optical gain than $1.3{\mu}m$ GaAsSb/InGaNAs/GaAs trilayer quantum well structure. This means that GaAsSb/InGaNAs/GaAs system is promising as long-wavelength optoelectronic devices for optical communication.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.401-404
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• 1998

Recently, InGaP/GaAs HBTs have been much interested as a potential replacement for AlGaAs/GaAs HBTs because of their superior device and material properties. In this paper, DC characteristics of InGaP/GaAs HBTs and the temperature dependance as well as the reliability were investigated comparing with AlGaAs/GaAs HBTs. As a results InGaP/GaAs HBTs produced the superior performance to AlGaAs/GaAs HBTs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.6
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• pp.282-288
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• 2017

In this paper, GaAs/AlGaAs multi-layer structure was grown by liquid phase epitaxy with graphite sliding boat, which can be used as a device structure of a photocathode image sensor. The multi-layer structure was grown on an n-type GaAs substrate in the sequence as follows: GaAs buffer layer, Zn-doped p-type AlGaAs layer as etching stop layer, Zn-doped p-type GaAs layer, and Zn-doped p-type AlGaAs layer. The Characteristics of GaAs/AlGaAs structures were analyzed by using scanning electron microscope (SEM), secondary ion mass spectrometer (SIMS) and hall measurement. The SEM images shows that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure was grown with a mirror-like surface on a whole ($1.25mm{\times}25mm$) substrate. The Al composition in the AlGaAs layer was approximately 80 %. Also, it was confirmed that the free carrier concentration in the p-GaAs layer can be adjusted to the range of $8{\times}10^{18}/cm^2$ by hall measurement. In the result, it is expected that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure grown by the LPE can be used as a device structure of a photoelectric cathode image sensor.

• Korean Journal of Environmental Agriculture
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• v.5 no.1
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• pp.35-42
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• 1986

This study was carried out to investigate the distribution of arsenic (As) fractions in paddy soils in relation to some soil characteristics and to find out the relationship between As fractions in soil and As content in brown rice. Soils and rice samples were collected from paddy field adjacent to arsenic mining and refinery sites. Sequential extraction procedures were used to fractionate As in soils into the designated forms of water soluble-As, Al-As, Fe-As, Ca-As, and residual-As. The results obtained were as follows: 1. The percent distribution of As fractions in soil showed a wide difference depending on some soil properties. The relative abundance of the extractable inorganic As fractions was in the order of Fe-As>Al-As>Ca-As>Water soluble-As regardless of mining and refinery sites. Residual-As fraction was more abundant in mining site than in refinery site. 2. With increasing soil pH, the percent distribution of Fe-As and Al-As fractions were decreased, but that of Ca-As and Residual-As fractions increased. The percent distribution of Al-As fraction in soil was negatively correlated with soil CEC, but others showed positive relationships. 3. Active Al and Fe content, and exchangeable Ca content in soil were positively correlated with the percent distribution of Al-As, Fe-As, and Ca-As fractions in soil respectively, and higher correlation between them was shown in mining site than in refinery site. 4. Soil As fractions, except for water soluble-As, showed significant correlation with among each others and also with 1N HCl extration method using as the common soil As extractant in Korea. 5. Arsenic content in brown rice had highly significant correlation with Al-As fraction in soil and it also showed significant correlation with Fe-As and Ca-As fractions, Total-As, and 1N-HCl extractable As.

• Language and Information
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• v.19 no.1
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• pp.37-57
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• 2015

This paper is primarily intended to provide a new insight on which the structural properties of As-Parenthetical constructions shown by Potts (2002) might be regarded as cross-linguistically common one. As a first attempt, it introduces the characteristics of Korean As-Parenthetical by carefully investigating them through the data, focusing on the similarities or differences between two languages with a constructional theoretical perspective. The paper here provides three properties of Korean as-clauses in the morphological and syntactic aspects. First, the morpheme 'as' in English as-clause would be realized as three different morphemes as a bound one. Korean as-clauses can be introduced by three different morphemes, '-tusi, -chelem, -taylo' and unlike that in English as-clauses, they behave as bound morphemes which do not stand alone. Even though they are attached into different morpho-syntactic stems, they do not make any meaning change only under this clause. Secondly, two syntactic types of as-clauses can also be found in Korean, similarly to those of English: CP-As type and Predicate-As type, depending on which types of gap they involve in. English has one more subtype of Predicate-As type (called inverted Predicate-As clause), while Korean does not show this subtype. Thirdly, the various mismatches attributed by the gap and the antecedent come from the constructional restrictions of as-clauses in Korean. In addition, the paper attempts to display various ambiguities from the as-clauses through disjoint references or negative sentences in As-Parenthetical constructions.

• Economic and Environmental Geology
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• v.36 no.5
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• pp.349-356
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• 2003

As industrial activities are growing, pollutants found in the contaminated land are getting diverse. Some contaminated areas are subject to mixed wastes containing both organic and inorganic wastes such as hydrocarbon and heavy metals. This study concerns with the influence of the degradation of organic pollutants on the coexisting heavy metals, expecially for As. As mainly exists as two different oxidation state; As(III) and As(V) and the conversion between the two chemical forms may be induced by organic degradation in the soil contaminated by mixed wastes. We operated microcosm in an anaerobic chamber for 60 days, using sandy loam. The soils in the microcosm are artificially contaminated both by tetradecane and As, with different combination of As(III) and As(V); As(III):As(V) 1:1, As(III) only and As(V) only. Although not systematic, ratio of As(III)/As(Total) increase slightly at the later stage of experiment. Considering complicated geochemical reactions involving oxidation/reduction of organic materials, Mn/Fe oxides and As, the findings in the study seem to indicate the degradation of the organics is connected with the As speciation. That is to say, the As(V) can be reduced to As(III) either by direct or indirect influence induced by the organic degradation. Although Fe and Mn are good oxidising agent for the oxidation of As(III) to As(V), organic degradation may have suppressed reductive dissolution of the Fe and Mn oxides, causing the organic pollutants to retard the oxidation of As(III) to As(V) until the organic degradation ceases. The possible influence of organic degradation on the As speciation implies that the As in mixed wastes may be have elevated toxicity and mobility by partial conversion from As(V) to As(III).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.146-147
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• 2012

InP 기판위에 자발성장법으로 성장된 InAs 양자점은 $1.55{\mu}m$ 영역에서 발진하는 양자점 반도체 레이저 다이오드 및 광 증폭기를 제작할 수 있기 때문에 많은 관심을 받고 있다. 광통신 대역의 $1.55{\mu}m$ 반도체 레이저 다이오드 및 광 증폭기 분야에서 InAs/InP 양자점이 많은 관심을 받고 있으나, InAs/GaAs 양자점에 비해 제작이 어려운 단점을 가지고 있다. InAs/InP 양자점은 InAs/GaAs 양자점에 비해 격자 불일치가 작아 양자점의 크기가 크고 특히 As 계 박막과 P 계박막의 계면에서 V 족 원소 교환 반응으로 계면 특성 저하가 발생하여 성장이 까다롭다. As 과 P 간의 교환반응은 성장온도와 V/III 에 의해 크게 영향을 받는 것으로 보고되었다. 그러나, P계 InGaAsP 박막 위에 InAs 성장 시 발생하는 As/P 교환반응에 대한 연구는 매우 적다. 본 연구에서는 InGaAsP 박막 위에 InAs 양자점 성장 시 GI (growth interruption)에 의한 As/P 교환반응이 InAs 양자점의 형상 및 광학적 특성에 미치는 영향을 연구하였다. 시료는 수직형 저압 Metal Organic Chemical Vapor Deposition (MOCVD)를 이용하여 $520^{\circ}C$의 온도에서 성장하였다. 그림1(a) 구조의 양자점은 InP (100) 기판위에 InP buffer layer를 성장한 후 InP와 격자상수가 일치하는 $1.1{\mu}m$ 파장의 InGaAsP barrier를 50 nm 성장하였다. 그 후 As 분위기 하에서 다양한 GI 시간을 주었고 그 위에 InAs 양자점을 성장하였다. 양자점 성장 후 InGaAsP barrier를 50 nm, InP capping layer를 50 nm 성장하였다. AFM측정을 위해 InP capping layer 위에 동일한 GI 조건의 InAs/InGaAsP 양자점을 성장하였고 양자점 성장 후 As분위기 하에 온도를 내려주었다. 그림1(b) 구조의 양자점은 그림1(a) 와 모든 조건은 동일하나 InAs 양자점과 InGaAsP barrier 사이에 GaAs 2ML를 삽입한 구조이다. 양자점 형상 특성 평가는 Atomic force microscopy를 이용하였으며, 광특성 분석은 Photoluminescence를 이용하였다.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.421-426
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• 1999

In this paper, we present p-channel GaAs MOSFET having $Al_2O_3$ as gate insulator fabricated on a semi-insulating GaAs substrate, which can be operated in the depletion mode. $1\;{\mu}m$ thick undoped GaAs buffer layer, $4000\;{\AA}$ thick p-type GaAs epi-layer, undoped $500{\AA}$ thick AlAs layer, and $50\;{\AA}$ thick GaAs cap layer were subsequently grown by molecular beam epitaxy(MBE) on (100) oriented semi-insulating GaAs substrate and this wafer was oxidized. AlAs layer was fully oxidized as a $Al_2O_3$ thin film. The I-V, $g_m$, breakdown charateristics of the fabricated GaAs MOSFET showed that wet thermal oxidation of AlAs/GaAs epilayer/S I GaAs was successful in realizing depletion mode p-channel GaAs MOSFET.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.89-90
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• 2010

최근 우리는 InGaAs 위에 성장한 InAs 양자점에 GaAs를 얇게 덮음으로써 양자고리를 성장하고, 그 광학적 특성을 분석하였다. [1] 이번 연구에서는 이 양자고리 구조의 전자 구조 및 광학적 특성을 전산모사를 통해 계산하였고, GaAs가 구조의 응력, 압전 포텐셜 및 light-hole 분율에 미치는 영향을 분석하였다. 이론적인 분석을 위해, valence force field 방법을 이용하여 이종 물질간의 격자상수 차이에 의한 격자 변형 및 압전 포텐셜의 변화를 계산하였고, 양자고리 내 전자의 양자화 에너지 및 파동함수를 k p 방법을 통해 얻을 수 있었다. 또한 광학적인 특성 등의 다체 효과를 예측하기 위해 configuration interaction 방법을 사용하였다. 이 연구에서 우리는, GaAs가 InAs에 강한 압축 응력을 가할 것이라는 일반적인 예측과 달리, InGaAs 매트릭스 안에서는 격자상수가 작은 GaAs가 InAs 양자고리에 효과적인 압축 응력을 가할 수 없음을 보였다. 특히 GaAs 층의 두께가 얇을 경우, InGaAs 매트릭스에 의해 인장 응력을 받는 GaAs가 InAs의 응력을 해소하기 충분한 공간을 제공하여, 오히려 InAs의 압축 응력을 약화시키는 것을 알 수 있었다. 이 연구 결과는 응력 분포가 단순한 양자우물 등의 2차원 구조와 달리, 응력 분포가 복잡한 3차원 나노 구조에서는 단순히 격자상수만으로 파장 변화 경향을 예측할 수 없음을 나타낸다. 또한 우리는, GaAs의 큰 negative 이방 응력과 InAs의 작은 positive 이방 응력에 의해 전자와 heavy-hole은 InAs에, light-hole은 GaAs에 구속됨을 보였다. 즉, InAs보다 밴드갭이 큰 GaAs가 전자와 heavy-hole에 대해서는 강한 포텐셜 배리어로 작용하지만 light-hole에 대해서는 포텐셜 우물로 작용하는, 반 우물-반 배리어 특성을 가짐을 알 수 있었다. 이로 인해 GaAs가 있는 양자고리의 light-hole 분율이 GaAs가 없을 경우에 비해 2배에서 8배가량 증가함을 보일 수 있었다. 비슷한 특성이 hole에 대해서는 InP나 InGaAsP 위에 성장한 GaAs 층에서 보고된 바가 있으나, 전자는 InAs로, hole은 GaAs로 분리할 수 있는 3차원 나노 구조에 대한 연구는 이 연구가 처음이다. [2]

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.1
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• pp.1-7
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• 2000

In this paper, we present n-channel GaAs MOSFET having $Al_2O_3$ as gate in insulator fabricated on a semi-insulating GaAs substrate. 1 ${\mu}$m thick undoped GaAs buffer layer, 1500 ${\AA}$ thick n-type GaAs, undoped 500 ${\AA}$ thick AlAs layer, and 50 ${\AA}$ GaAs caplayer were subsequently grown by molecular beam epitaxy(MBE) on (100) oriented semi-insulating GaAs substrate oxidized. When it was wet oxidized, AlAs layer was fully converted $Al_2O_3$. The I-V, $g_m$, breakdown charateristics of the fabricated GaAs MOSFET showed that wet thermal oxidation of AlAs/GaAs epilayer/S${\cdot}$I GaAs was suitable in realizing depletion mode GaAs MOSFET.